首先的英语高级表达有

1.in the first place
2.first
Relative explainations:
3.begin.with
4.for one thing.(for another)
5.first of all
6.to begin with
7.imprimis
8.in the first instance
9.firstly
10.of all things
11.above all
12.to start with
13.primarily
14.threshold
15.at a first brush
16.first and foremost
17.the first thing
18.in the beginning
Examples:
那不是个好办法,首先没人会帮我们的忙.
It is not a good idea.For one thing,nobody will help us.
我首先是一个教师,其次才是一个作家.
I am a teacher in the first place and a writer in the next place.
婚姻首先是一种契约,它必须以公正为制约.
Marriage is,first of all,a contract which must be governed by justice.